The present invention relates to mountings for supporting antennas above surfaces such as roof surfaces.
A mounting for securing an antenna above the surface of a building roof or the like should satisfy several demanding and apparently conflicting objectives. The mounting must be capable of supporting the weight of the antenna, and must also withstand the loads imposed by the environment, such as snow loads and wind loads applied to the antenna. Building roof structures typically are designed to take distributed loads such as the pressures exerted by snow or wind on the roof, and hence are not capable of bearing substantial concentrated loads. As it is typically impractical to reinforce an existing roof structure, the antenna mounting should be arranged to distribute the loads associated with the antenna over a large area of the roof structure.
The mounting should also be arranged to hold the antenna firmly in position, and to resist deflection of the antenna under the influence of environmental loads such as wind. This requirement is particularly stringent in the case of mountings for dish type reflector antennas. These antennas typically are aimed at a specific remote station, such as an earth satellite. The performance of such an antenna will be severely impaired if antenna movement disturbs the preset aim. Moreover, these dish antennas present very large areas to the wind, and hence are exposed to large deflecting forces. Uneven wind forces created by eddy currents or vortexes generated at the edges of a dish antenna tend to twist the antenna. The antenna mounting structure thus must be sufficiently rigid to maintain the aim of the antenna despite these forces and torsional moments.
The antenna mounting structure also should be arranged to minimize damage to the roof in installation. Thus, the mounting structure should be arranged so that it can be secured to the roof without making holes in the roof or with only a few, small holes in the roof. Further, the antenna mounting structure should be arranged so that it can be carried to the roof by one worker. Therefore, the mounting structure should be provided in the form of separate parts, none of which is heavier than about 50 lbs. However, the assembly of these parts should be simple and easy so that the mounting structure can be assembled conveniently on the roof. Moreover, the mounting structure should be arranged to compensate for differences in the pitch or slope of the roof, and to work well with flat roofs or pitched roofs. The mounting structure should also be arranged to compensate for minor irregularities in the roof surface.
All of these factors, taken together, present a formidable challenge, which has not been met satisfactorily heretofore. Accordingly, there are needs for improved antenna mounting structures, and particularly for mounting structures suitable for supporting a dish antenna on a roof structure.